Cross-country skiing differs substantially from downhill skiing in that the course for the cross-country skier is not always downhill. In fact, cross-country skiers are often faced with the problem of how to ski uphill. This problem has led to the development of many wax concoctions that can be applied to selectively increase or decrease the frictional grip between the ski bottom runners and the snow surface. Some mechanical appliances have also been developed to enhance traction of skis.
Both approaches have had serious drawbacks. Wax is difficult and time consuming to apply. It is very temperature dependent so slight temperature changes can render some waxes useless. The skier must then stop, remove the skis, scrape the old wax from the skis and apply a different formula wax for the particular temperature. By this time, the temperature may have changed again. Some waxes are best suited for wet snow while other waxes are suited for dryer snow. Additionally, wax that gives good traction climbing uphill has an adverse effect when the skier wants less traction in a downhill run.
Mechanical appliances would seem to be a solution to the difficulties presented with application of wax to cross-country ski runners. One solution has been the "fish scale" surface provided on many forms of cross-country ski runners. The "scales" theoretically allow a relatively free sliding motion in a forward direction while gripping the snow surface to prevent rearward sliding motion of the ski. The quantity of these scales required to produce a desirable effect, however, results in a higher coefficient of friction for forward sliding motion than what normally may be desired. Furthermore, the surface will wear and cannot be easily replaced or reconditioned. When the "fish scale" ski runners wear down, the skis must usually be disposed of. This is both wasteful and expensive to the skier.
U.S Pat. No. 4,027,895 to Larsson discloses a cross-country ski having alternate sliding and holding surfaces. This is a specially designed ski having two separate runner surfaces. One surface may be elevated above the other when not in use and subsequently lowered to engage the snow while the other is simultaneously raised. Both runner surfaces are covered with a "grease" or wax typically used for normal cross-country skis. One surface is covered with a high friction "grease" while the other with a low friction material. The surfaces alternately engage and disengage the ground of snow surface due to action of the skier in raising and lowering his or her heel.
U.S. Pat. No. 1,783,833 to Elsner discloses a strap-on, non-slip device used with skis. This device can be attached and removed selectively from skis. When attached, the device functions constantly to provide a high friction surface on the ski runners.
A mechanical climbing and braking device for skis is disclosed by Tribelhorn in U.S. Pat. No. 2,844,380. This is a relatively complex inset mechanism for skis using springs, cams, and lever mechanisms. The lever mechanisms can be operated to shift traction members to operative positions projecting from the bottom surfaces of the ski or to inoperative positions retracted within housings on the ski. The traction devices work against motion of the ski in both foward and rearward directions. In the forward direction the traction devices work as brakes to slow foward progress of the skier. The skier must release the traction devices and retract them to inoperative positions before the ski can slide freely in the forward direction. But, the ski is also free to slide rearwardly when the traction devices are retracted.
U.S. Pat. No. 2,120,363 to Jerns discloses a traction device that is stored on the top of a ski and can be shifted from a storage position at the top of the ski to an operative position projecting downwardly into the snow beneath the ski. A locking arrangement will secure the traction device in either the operative or inoperative positions.
A ski and snowshoe device is disclosed in U.S. Pat. No. 3,927,896 to Detoia. The traction device used here is integral with the ski and includes traction members that can be pivoted through openings in the ski downwardly to engage the snow surface. The traction devices are actuated by pressing a lever downwardly and are lifted by releasing a latch to allow the devices to swing back upwardly to inoperative positions. A somewhat similar upward or downward latching traction mechanism is disclosed in U.S. Pat. No. 3,582,101 granted to Roger Ste. Marie.
An improved mechanical device is disclosed in U.S. Pat. No. 2,358,213 to Courage. Mr. Courage discloses a traction device for skis that pivot in response to motion of the ski in forward and rearward directions. When the ski is moved forwardly, the traction device will swing upwardly and engage the bottom runner surface of the ski where it will produce less drag. Then, when the ski is thrust rearwardly, the device will pivot downwardly to an operative position to dig into the snow, preventing rearwardly sliding motion of the ski. The device is removable from the ski due to the forward drag it presents by obstructing the smooth bottom runner surface of the ski when in place.
Of the above references, none have provided a completely satisfactory solution to the problem of providing maximum traction while skiing on flat ground or uphill situations and minimum traction while skiing downhill. The wax arrangements are difficult and temperature dependent while the mechanical appliances produce additional drag during the downhill run. The problem therefore has remained of obtaining some form of traction device for skis that will resist rearward sliding motion of the ski while allowing free forward sliding motion thereof.